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Using Netty in Java

Netty is a high-performance networking framework for building server-side and client-side applications in Java. It provides a flexible and event-driven architecture for handling network communication efficiently. Netty is commonly used for building scalable and low-latency network applications, such as web servers, proxy servers, and messaging systems.

We've implemented a code sample that you can re-use to convert your HTML documents to PDF, JPG, PNG or WEBP using PDFShift and Java:

import io.netty.handler.codec.http.*;
import io.netty.buffer.Unpooled;
import io.netty.util.CharsetUtil;

import java.util.HashMap;
import java.util.Map;


public class Convert {
    private static final String API_KEY = "api:sk_XXXXXXXXXXXXXX";
    private static final String HOST = "";
    private static byte[] convert(String apiKey, Map<String, String> params, String endpoint) throws Exception {
        if(!Arrays.asList("pdf", "png", "jpg", "webp").contains(endpoint)) {
            throw new IllegalArgumentException("Invalid endpoint");

        String url = HOST + endpoint;
        String paramsJson = new Gson().toJson(params);

        FullHttpRequest request = new DefaultFullHttpRequest(
                HttpVersion.HTTP_1_1, HttpMethod.POST, url,
                Unpooled.copiedBuffer(paramsJson, CharsetUtil.UTF_8));

        request.headers().set(HttpHeaderNames.CONTENT_TYPE, "application/json");
        request.headers().set(HttpHeaderNames.AUTHORIZATION, apiKey);

        HttpClient client = new HttpClient();
        FullHttpResponse response = client.sendRequest(request);

        if (!HttpResponseStatus.OK.equals(response.status())) {
            throw new RuntimeException("Failed : HTTP error code : " + response.status());

        if (params.containsKey("filename") || params.containsKey("webhook")) {
            Map<String, Object> responseMap = new Gson().fromJson(
                    new TypeToken<Map<String, Object>>() {
            return responseMap;

        return response.content().array();

Here's how you can use the above code:

public static void main(String[] args) {
    Map<String, String> params = new HashMap<>();
    params.put("source", "");
    byte[] result = convert(API_KEY, params, "pdf");
    Files.write(Paths.get("result.pdf"), result);

We've tested this code with the latest version of Netty and it's ready to be used in your project.

But if you were to encounter any bugs or issues while running it (or if you want to suggest changes to improve the code), please contact us and we'll be happy to help you out.